Nitrospira

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A Microbial Biorealm page on the genus Nitrospira

Nitrospira. Courtesy of Englewood.

Classification

Higher order taxa:

Bacteria; Nitrospirae; Nitrospira (class); Nitrospirales; Nitrospiraceae; Nitrospira

Species:

Nitrospira marina, N. moscoviensis, N. sp.

NCBI: Taxonomy Genome

Description and Significance

Nitrospira are nitrite-oxidizing bacteria that are important in marine habitats. In aquariums, for example, if the ammonia/nitrite/nitrate cycle is thrown off, the ecosystems suffers and fish can get sick or die. Therefore, nitrite-oxidizing bacteria as well as the other bacteria in this system are important for healthy marine ecosystems. In addition, Nitrospira-like bacteria are the main nitrite oxidizers in wastewater treatment plants and in laboratory scale reactors, not Nitrobacter sp., as was previously thought.

Genome Structure

Projects to sequence the genome of Nitrospira-like organisms are being undertaken by organizations such as the University of Vienna: Institute of Ecology and Conservation Biology, in order to analyze the nitrite-oxidizing mechanisms and the Nitrospira ability to compete with other nitrite-oxidizing bacteria. Also starting on the genome of Nitrospira marina Nb-295 is the The Gordon and Betty Moore Foundation Marine Microbiology Initiative, and J. Craig Venter Institute.

Cell Structure and Metabolism

Cell aggregate of Nitrospira-like bacteria detected by fluorescence in situ hybridization (FISH) in biofilm from a wastewater treatment plant. Source: Daims et al., Appl. Environ. Microbiol. 67(11):5273-5284

Uptake of pyruvate, detected by FISH-microautoradiography, by ammonia-oxidizing bacteria (green) and Nitrospira-like bacteria (red) in biofilm. Black spots indicate uptake of radioactively labeled pyruvate. Source: Daims et al., Appl. Environ. Microbiol. 67(11):5273-5284

Nitrospira is a chemolithoautotrophic nitrite-oxidizing bacterium that is generally found in freshwater or saltwater. Nitrospira-like bacteria take up inorganic carbon (like HCO₃^- and CO₂) as well as pyruvate under aerobic conditions. They can not use acetate, butyrate, or propionate, however. Nitrospira have doubling time of every 12 - 32 hours.

Ecology

The biogeochemical nitrogen cycle. Source: Dept. of Microbial Ecology, University of Vienna

Nitrospira can live in marine or nonmarine habitats. It has been isolated from ocean water, freshwater, aquarium water, deltaic sediment, deep-sea sediments, soils, and an iron pipe of a heating system (Daims et al. 2001). Nitrospira is part of a nitrification process which is important in the biogeochemical nitrogen cycle. Nitrification is the oxidation of ammonia to nitrite by autotrophic bacteria of the genus Nitrosomonas and oxidation of the nitrite to nitrate by bacteria in the genus Nitrobacter or Nitrospira. This is important in marine environments because too much ammonia or nitrite can cause death in fish. However, Nitrospira and similar bacteria are slow-growing organisms, which means that a newly set-up aquarium without an established population of these bacteria can accumulate toxic concentrations of ammonia and nitrite. In an attempt to fix this problem, commercial companies have tried to market special preparations of ammonia-oxidizing and nitrite-oxidizing bacteria (the mixes included Nitrobacter instead of Nitrospira) that could be put into a new aquarium to establish a healthy nitrogen cycle. However, these mixes were inexplicably ineffective so tests were done to analyze the bacterial content of aquaria water. While bacteria from the genus Nitrobacter are nitrite-oxidizing organisms and could theoretically fill the nitrite-oxidizing niche, the tests indicated relatively high numbers of Nitrospira and no Nitrobacter bacteria at all. Thus, Nitrospira is now considered the dominate nitrite-oxidizing bacterium in aquariums, (as well as in wastewater treatment systems and other reactors as shown by other similar studies) (Hovanec et al.1998). Though water that is too rich in ammonia or has a pH that is too low will inhibit Nitrospira's nitrifying activity.